The management of diaphyseal forearm fractures has undergone evolutions over the years, with ORIF being the gold standard for adult patients. However, the search for a less invasive technique and the favorable results with long bone IMN treatment has led to the advent and application of the anatomical interlocking IMN systems. Our systematic review’s main finding suggests that clinical outcomes of IMN are satisfactory and comparable to ORIF with plates, achieving similar complication rates (16.7% versus 14.9%).

There were a number of implants used in the studies, all unified by an anatomical design and interlocking screws to ensure rotation stability. The overall patient reported outcome measures were favorable for both IMN and ORIF with no statistically significant difference (DASH: 10.1 ± 4 versus 13.1 ± 6) (p = 0.28). In addition, both techniques achieved functional arcs of motion, with aggregate values that were higher for ORIF than IMN. Due to the inconsistent reporting of range of motion, a subgroup analysis was not feasible to determine whether there was a significant difference between groups. While this finding may suggest that patients undergoing ORIF are more likely to recover a full arc of motion, firm conclusions cannot be drawn unless fracture types are matched. Comparative studies by Kibar et al., Lee et al., and Behnke et al. show little difference between the groups [12, 14, 15]. Nearly all studies included a variety of fracture types according to the AO classification.

The meta-analysis revealed a significantly shorter operative time in the IMN group (50.8 ± 17.7 min) compared with the ORIF group (65.3 ± 28.7 min). This finding was consistent across all the included studies [10, 15,16,17]. Zhang et al. reported a mean operative time of 137 min for ORIF and 77 min for IMN. They attribute this to a smaller incision with less soft tissue dissection that may be particularly beneficial to cases that are time sensitive from a physiological standpoint.

The data suggest that IMN may have some advantages over ORIF. Nail fixation can be a suitable choice in patients with poor overlying skin that may result in infection or dehiscence requiring coverage [6, 12, 15]. Further, it is suggested that they may be of particular use in addressing highly comminuted or segmental fractures that are unlikely to be reduced anatomically with ORIF [12]. However, the efficacy of utilizing closed or minimal-access techniques to achieve adequate reduction and rotation are as of yet unclear. Some studies suggested that employing IMN as a less invasive yet rotationally stable construct carries high union rates and could reduce the risk of infection [14, 18,19,20].

A notable observation is the absence of refractures following the removal of intramedullary nails. Earlier studies have reported refracture rates after plate removal ranging from 5% to 20% [21, 22]. Removal of a nail does not necessitate repeat surgical dissection and does not leave as many areas of bone voids after screw removal. In addition, although scar cosmesis may be less of a concern to the orthopedic surgeon [23], Lee et al. reported lower satisfaction scores attributed to large scars in female patients receiving ORIF compared with IMN [15].

Although promising, use of IMN for forearm fractures is still relatively novel for most surgeons. The pre-contoured nails may require bending and additional contouring to match the variable patients’ native radial bow [24, 25]. Nails are unlikely to restore and maintain the anatomic bow as well as plates do, especially if closed reduction was performed [10, 13, 15]. However, residual angulation of less than 10° in any plane is unlikely to result in functional impairment [2]. Importantly, the concept of using nails for forearm fractures means that “relative stability” is achieved, defying the traditional dogma of the need for compression and anatomical reduction for the management of these fractures. Unfortunately, our review was unable to provide clear information on how many of the cases required some sort of an open incision to facilitate reduction. While general reporting regarding this was deficient, Saka et al. reported that 27% (16 out of 59 patients) required reduction via mini-incisions [26].

Hybrid fixation may provide some flexibility to surgeons in preoperative decision-making and seems to be an attractive tool. For instance, IMN can be utilized where the soft tissue envelope appears unfavorable [10, 12]. Zhang et al. found that the best results were achieved by nailing the ulna and plating the radius [10]. Further, plating still possesses the advantage of anatomical reduction in the radius. Although IMN are evolving and results are promising, surgeons should establish realistic expectations in line with the potential complications of using IMN in the forearm [27].

Our dataset underscores the need for caution to avoid recurrent complications. Notably, 11 instances of EPL ruptures were linked to IMN, necessitating reoperations for extensor pollicis longus reconstructions and tendon transfers, primarily diagnosed 2–6 weeks post-surgery. These injuries were often traced back to an ulnar entry point violating the third extensor compartment and creating bony spurs from Lister’s tubercle [12, 18, 28]. Thus, proper visualization, a more radial entry point, and hardware that is not prominent may mitigate this risk [12, 17, 18, 28]. Nerve palsies, impacting roughly 1% of IMN cases, were treated conservatively, though their precise cause remains elusive in most studies [10, 14, 19]. The IMN group saw a higher rate of delayed union at 3.1% versus 1% in ORIF, with the majority of reoperations addressing nonunions and EPL injuries.

This systematic review is subject to several limitations. Variations in study design, patient demographics, and the types of implants used across the included studies could potentially impact outcomes. A notable gap in the literature is the inconsistent reporting on postoperative protocols, rehabilitation, and institutional protocols, which were not controlled for in the studies. The interpretation of results is further complicated by the lack of standardized reporting on complications and follow-up durations. Additionally, the predominance of retrospective studies introduces potential biases.

Several factors may affect outcomes across the studies, including patient characteristics such as age, medical comorbidities, and osteoporosis. The recent introduction of the IMNs poses a limitation on the availability of long-term data. Furthermore, despite all implants sharing locking and anatomical features, there are limited data on how anatomical these nails truly are, whether they required contouring, and the stability each type achieves. Another area of concern is the nature of healing achieved; if nailing is performed without anatomical reduction and compression, it may result in secondary healing with callus formation. It would be valuable to explore whether the formation of a callus interferes with the range of motion.

The techniques employed by surgeons, particularly in terms of reduction methods (closed or open), were poorly reported and could influence infection rates and healing, especially if extensive soft tissue dissection occurred. Furthermore, a distinction in outcomes between closed reduction techniques and open techniques is necessary, as minimally invasive open techniques may have a higher likelihood of nerve injuries. In addition, studies should attempt to report the frequency of closed reduction attempts before converting to open reduction. Thus, complications for both approaches should be reported to determine whether closed reduction truly achieves proper reduction and rotational alignment.

As such, future research should scrutinize IMN outcomes across matched fracture types and severities. There would clearly be a learning curve associated with the technique, and determining techniques to address simple versus comminuted fractures is important. Furthermore, detailed descriptions of reduction techniques are warranted. It is crucial to discern whether any adjunctive measures, such as mini-incisions or open reductions, were employed alongside nailing. Furthermore, studies have largely overlooked the financial implications and cost-effectiveness of IMN compared with traditional plating methods.